Brownfield Briefing

Has risk assessment finally come of age?

- By: ,

Courtesy of Brownfield Briefing

Sarah Dack, principal risk assessor, and James D Nelson, associate for risk assessment & modelling, of Mouchel look at the strides risk assessment has taken in recent years.

In the mid 90s the number of quantitative human health risk practitioners in the UK could be counted on your fingers. Industry was screening against ICRCL/Kelly tables (often based on the tables, without the accompanying documentation) and the word ‘risk’ was often missing. In February 2002, CLEA was launched and risk assessment had a truly UK approach.

Once the euphoria dissipated, it appeared consultancies and regulators had returned to screening, based on Soil Guideline Values (SGVs). Many Environmental Health Officers were expected to know all about risk assessment with minimal training. As a result some baulked at information derived from non-CLEA2002 models and non-standard scenarios. We demanded more SGVs, felt we understood risk assessment, but generally we screened. Industry blamed the regulators, the regulators blamed industry, and everyone was baffled by SPOSH, until the ‘Way Forward’ was published.

We now have new guidance and new CLEA software. In August 2008, SR2, SR3, SR4 and SR7 were launched, and in January 2009, SR2, SR3 and SR4 were amended and CLEA v1.04 was released. We now have SGVs for 10 contaminants and their isomers. CIEH/LQM have brought out Generic Assessment Criteria (GACs) for 81 contaminants including fractions and isomers and the Environmental Industries Commission are soon to bring out more GACs. The correspondence on Jiscmail – an email discussion forum for contaminated land issues – has included new values for ‘review’ by the wider community.

Discussions occur on chemical parameters, and the use of appropriate soil organic matter, not on whether anyone has a GAC for Benzo(a)pyrene.

Perhaps we have come full circle. Now it’s not a handful of risk assessors, but a wider understanding of risk-based contaminated land assessment. Can we congratulate ourselves and the industry for taking ownership of risk assessment, instead of waiting for the regulator to ‘do something’? Perhaps. Now we can start meaningful discussions regarding risk-based assessment of contaminated land.

Now 2009 has seen EHOs and industry looking at the Soil Organic Matter (SOM) values and which are relevant. A discussion on whether 6% applies to contaminated sites, where topsoil is poor or doesn’t exist, has occurred. As a result CIEH/LQM and EIC GACs have been generated at 1% and 2.5% SOM and the 6% default. Therefore the use of SGVs as screening, regardless of SOM, has not occurred and consideration has been given to their relevance.

Similarly, consideration has been given to appropriate land uses and garden sizes. Ultimately, the increased use of public land for ‘guerrilla gardening’ will have to be considered further, and many local authorities are watching this with interest. Environmental Protection UK has published a fact sheet advising people on the risks from using public space and derelict land for vegetable growing. With publicity on Corby, maybe the public will think twice about this!

Discussion has started, and will become louder, on sub-surface soil to indoor air. The Environment Agency has provided a default of 10 as the Johnson & Ettinger model over-predicts vapour transport. CIEH/LQM have used this default for the TPHCWG. There are arguments for and against this for the heavier fractions, and they have not decreased the value to below one for the chlorinated solvents, which may be under-predicted.

Finally, we’ll have to see what the Health Protection Agency will decide regarding ‘minimal risk’. ALARP is too variable. Based on UK and international risk levels, anything between 1/1000 and 1/1000000 is acceptable. Without a decision on this, SPOSH is difficult to determine. Maybe if the HPA doesn’t decide soon, then the members of Jiscmail will.

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